Hi Sriram,Originally posted in cdnusers.org by EngHan
You can get many of the answer from the I/O pads data sheet. It will tell you how many pad-ring ground/power pads are needed. It is related to the number of output I/O pads you used, and the max distance from any pad to a pad-ring ground/power pads.
It is always necessary to read the I/O pad datasheet. For example, you might also have special pad, like osc pad, USB pad, PCI pad, analog power pad, power pad for efuse/flash/etc etc. There are always special layout requirements.
As for core power pad, a short answer is to run powermeter/voltagestorm to analyze IR drop and max current flow. As LiSiang point out, it is process and design related. Perform some early analysis and develop your own rule of thumb for a particular process and design. For a start, read the datasheet to get the max current a power/ground pad can provide. Then ask the designer what is the expected power consumption. Then multiple this number by a factor (you have to figure out this factor base on the experience you interact with the design team. Also, note that worst power usually occur during test mode). For power stripping, start from at least 20% of the core area is covered by metal stripe (excluding M1 stripe).